I need a way to find factorail for big numbers like 8479!

Thanks in advance

raju

A simple way.
Just multiply them out.

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We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

See Stirlings formula (equations 13 and 14 here)

RonL

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"It is proof of a base and low mind for one to wish to think with the masses or majority, merely because the majority is the majority"
--Giordano Bruno

That is only an approximation.

__________________
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

How many digits does 8479! have?

(Rhetorical question)

RonL

__________________
"It is proof of a base and low mind for one to wish to think with the masses or majority, merely because the majority is the majority"
--Giordano Bruno

Over 29,000.

25972686487041052159869258722936182200373790277711 48344797668281885988268302193747006721558615751528[...29429 digits...]00000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000

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Old mathematicians never die; they just lose some of their functions.

I can find how many zeros is has .

__________________
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.

i had this problems some weeks back. Stirlings function is probably the best for large factorials. But otherwise use this bit of code i wrote in java which is computationally efficient.


public double gammaln(float xx){
double x,y,tmp,ser;
double[] cof={76.18009172947146,-86.50532032941677,
24.01409824083091,-1.231739572450155,
0.1208650973866179e-2,-0.5395239384953e-5};
int j;
y=x=xx;
tmp=x+5.5;
tmp -= (x+0.5)*Math.log(tmp);
ser=1.000000000190015;
for (j=0;j <= 5;j++) {ser += cof[j]/++y;}
return -tmp+ Math.log(2.5066282746310005*ser/x);}


public double factorial(float n){
double value = gammaln(n + 1);
double answer = Math.exp(value);
return answer;}

This is based around a method of gamma approximation by C.lanczos. (Paper is called - (A precision approximation of the gamma function).

This method can also be used to find NON integer factorials

I think ur asking this for a question like "find the lowest common multiple" (LCM)

there is no need to use massive formulas unless the number is greater then 1trillion.

just use Prime factorisation.

eg. 4 = 2 power of 2
6 = 3 x 2
1001 = 7 x 11 x 13
etc...

take the number and find all possible prime numbers which go ito it. (see examples above)
then...

eg. find the lowest common multiple of 4, 2, 6
4 = 2 squared 2 = 2 and 6 = 2x3
therfore the number must contain 2 squared and 3.
= 2 squared x 3
= 12

find all prime factors of the numbers. and take the common ones out
eg. 2 squared and 2
only use 2 squared because 2 is within 2 squared

then multiply them together.


(i can go on but it would just be useless)

How does this relate to finding the factorial of a large number?

RonL

__________________
"It is proof of a base and low mind for one to wish to think with the masses or majority, merely because the majority is the majority"
--Giordano Bruno